Song repertoires of Northern Cardinal (Cardinalis cardinalis) populations in a neighboring sapling, pole, and saw-timber stands in eastern Texas were tape-recorded during the 1979 breeding season. Cardinals in each area used different syllable types and sang songs of varying duration and complexity. Cluster analysis and discriminant function analysis identified three distinct dialects, one for each of the three study areas. Cardinals in the sapling stand used a wider range of frequencies than did those in the saw-timber stand. 

Cardinals in the pole stand used a range of frequencies intermediate in size to that of either the sapling or saw-timber stands. For all three populations, the frequency with the greatest amplitude was about 2 100 Hz, a low frequency that carries better than high frequencies over long distances. 

In the stand that lacked a closed canopy, cardinals typically used syllables with considerable frequency modulation; however, in the two older stands cardinals seldom used extensive frequency modulation in their songs. 

Differential singing behavior of this nature probably enhances long-distance communication by minimizing excessive reverberation from canopy foliage. We suggest that some of the differences in syllable structure noted between the three cardinal dialects may be the result of selective pressures exerted by the acoustics of the environment.